This invention relates to the field of poly(N-vinyl lactam)-chitosan gels and more particularly to gels which are absorbent and may be skin adhering, which are flexible and contour-conforming, and which can be used for a variety of applications.
Chitosan is a deacetylated chitin, and is a linear polysaccharide of deacetylated N-acetyl-D-glucosamine. Chitosan has been used to absorb heavy metals from water and industrial waste streams, and as a dyeing assistant in photographic emulsions. Chitosan derivatives have also been used in cosmetics and conditioning agents, in hair setting lotions and shampoos as, for example, in U.S. Pat. Nos. 4,134,412 and 4,202,881, when neutralized with acids.
Poly(N-vinyl lactam) s such as polyvinylpyrrolidone (PVP) have been used, for example, in pharmaceuticals, in certain types of films and in some cosmetic products.
It has been known that polyvinylpyrrolidone forms complexes with polyurethanes to yield hydrophilic blends or alloys. U.S. Pat. No. 4,642,267 describes hydrophilic polymer blends of polyurethane and hydrophilic poly(N-vinyl lactam) prepared in solvent solution to provide slippery coatings when wet and which are water insoluble to some extent once cured by drying.
European Patent Application 107,376 describes tacky PVP gels which require the use of ionizing radiation for cross-linking. U.S. Pat. No. 4,646,730 describes a PVP/Silver Sulfadiazine hydrogel dressing in which electron beam radiation is required to cross-link the PVP and form a gel. In addition, magnesium trisilicate, hydrogen peroxide and/or polyacrylic acid are added for color stabilization. It is apparent that there would be an advantage in making skin-adhering gels in the absence of expensive equipment and/or processing.
Ring opening of pyrrolidone groups on PVP was described by H. P. Frank, "The Lactam-Amino Acid Equilibria for Ethylpyrrolidone and Polyvinylpyrrolidone", Journal of Polymer Science 12, 565-576 (1954) , and A. Conix and G. Smets, "Ring Opening in Lactam Polymers", J. Poly. Chem. 13, 221-229 (1955). The concept of ring-opened pyrrolidone groups is made use of in this invention to unexpectedly attain absorbent gels.
It is therefore an object of the invention to provide dermatologically-compatible gels having a hydrophilic absorbent property.
It is a further object to produce gels without a need for expensive equipment and/or processing.
It is another object to provide gels of poly(N-vinyl lactam) and chitosan derivatives which can be used in a variety of products such as cavity dressings, drug delivery patches, face masks and wound dressings.